The success of the Barghest, especially the version equipped with a heavy gauss rifle, spurred the Lyran Commonwealth to devise another quad design armed with a heavy gauss rifle. In addition, jump capability was added, as well as a heavier set of backup armament.
The Cusith, named for the legendary hound of Scotland, debuted with stunning effectiveness in the Skye region during the jihad.

The Cusith combines the heavy gauss rifle with a jump capable quad, resulting in a deadly medium range combat mech.
The Defiance Hammerfist provides the bulk of its striking power, capable of downing light and many medum mechs with a single hit.
Defiance extended range lasers round out its arsenal, providing reliable laser fire in event of the heavy gauss rifle running out of ammunition.
In an interesting move, the design team placed the HildCo jump jets in the Cusith's legs, taking a cue from the Stalking Spider. As a result, the Cusith almost glides through the air when it jumps. The streamlined shape of the mech helps amplify the sight, and many warriors are awed by the sight of 85 tons of battlemech gracefully sailing through the air, and then cutting loose with its heavy gauss rifle.
A few elite pilots have even mastered firing the heavy gauss while in mid air, angling their jump jets in such a way that the jump thrust cancels out the recoil from the heavy gauss.

During the jihad, an attacking Word of Blake force on Skye was pushing against a precarious 4th Skye Ranger position. A Cusith was eventually left holding the position against an entire Level II unit.
The Cusith pilot did not panic, instead bringing his mech into close combat with the Blakists. In a brutal pounding match, the solitary Cusith held up the Blakist attack for more than ten minutes, taking down four Blakist mechs.
The delay was fatal to the Blakist advance, and the sweeping Skye Ranger counterattack destroyed them.

Hauptmann Paul Lambert
The Cusith pilot who put in such a strong performance on Skye, Lambert was awarded the Honor of Skye for his actions.
A son of Skye, Lambert is utterly loyal to Duke Robert Kelswa-Steiner and the Free Skye Movement. A leftenant in the 32nd Lyran Guard when it was crushed on Hesperus in the last days of the civil war, Paul retained his commision by a pardon from the Archon, and was transferred to the Skye Rangers.
With Robert swearing his allegiance wholly to Archon Peter Steiner after the horrors of the jihad, Paul is determined to follow his liege lord in defending the Lyran Commonwealth against all threats.

The bulk of Cusiths produced by Defiance on Heperus has gone to the Skye Ranger and Arcturan Guard formations. The Archon has channeled more Cusith production towards the Skye Rangers, as a gesture of reconciliation after the civil war, and also to repay them for their selfless defense of the Lyran Commonwealth during the jihad.